The present invention relates to a shifting arrangement for a synchronized gear wheel change box of a motor vehicle, and, more particularly, to a shifting arrangement which provides simple and low-cost locking of shift rails with respect to each other and to the gearbox.
An actuating arrangement for a gear wheel change box is described in the journal, Sport Auto, April 1988, Page 127. The gear speeds are preselected by a first Bowden cable actuated by a gear shift lever. The individual gear speeds are shifted by a second Bowden cable by way of shift forks and synchronizer clutches. An actuating arrangement, as shown in DE-PS 31 25 632, is used as a connection from the shift forks to the preselector shaft and the shifting shaft actuated by the Bowden cables. The shifting shaft is provided with a radially projecting shift finger which engages in recesses of shift rails forming shifting paths. The shift rails operatively associated with the shift forks can be moved transversely with respect to the shifting shaft. The gear speeds are preselected by displacing the shift finger in the axial direction of the shifting shaft. The gear speeds can be shifted by the swivelling of the shift finger. The shift rails situated next to the selected shifting path are each blocked by cams which are constructed in one piece with the shift finger and, from the inside, rest against circular-arc-shaped wall parts of the shift rails.
In order to implement a precise shifting, it is also necessary, however, precisely to guide the respective shift rail to be actuated during the shifting operation and to lock the shift rail in the respective shifting position.
It is, therefore, an object of the present invention to provide a simple locking arrangement at low cost and, through which, all shift rails can be locked with respect to one another and with respect to the gearbox.
The foregoing objects have been achieved in accordance with the present invention by locking respective shifting positions of the shift rails by a spring which form-fittingly and elastically engages in all the shift rails. Since the spring is non-displaceably fastened to the gearbox or to a component rigidly connected therewith, the mutual position of the shift rails and their position with respect to the gearbox is clearly established.
Another advantageous feature of the present invention is the spring having a U-shaped cross-section, in a tong-like manner with U-legs. The spring reaches around the top and bottom surfaces of the shift rails, and beads at the ends of the U-legs, engage in corresponding indentations of the shift rails. Advantageously, the indentations are each situated on two cam elevations respectively mounted on the shift rails and determine a neutral center position, a left shifting position and a right shifting position. The indentations and cam elevations at the holding rails may be punched out together with a V-recess. The stop cams of a shifting piece rest against the V recess. When a shift rail with the shift finger of the shifting piece is brought into a left or right shifting position, the spring lifts off the other shift rails during this shifting operation. However, these shift rails are locked because the stop cams rest against their V-recesses.